Concrete slab surface repair

[sennafan]

I am discussing repair of the surface of exterior slabs on grade with a property owner. The slabs were exposed to 2 or 3 unknown chemicals that have discolored and mildly etched the surface. The owner is adamant that no coatings or cementitious overlays be used for fear of poor long term performance. When I suggested sand blasting and/or grinding, he questioned whether the durability would be decreased.

I suspect we will only lose 1/16" to 1/8" of the surface to get rid of the effected concrete. The area is prone to freeze thaw and extremes of hot and cold weather. My thinking is that, if anything, blasting or grinding should remove the upper layer of cement paste and leave a stronger, possibly less porous surface unless we uncover air voids from poor consolidation or voids any exposed aggregate. Any thoughts or references to support or argue against my thoughts on this?

Thanks

 

[GeoPaveTraffic]

State highway departments often remove the top 1/16 to 1/2 inch of interstate pavements, it's called diamond grinding and they do it to improve ride quality. I can't imagin them doing that if the durability would be decreased.

As for using sand blasting, that could cause micro-cracks in the near surface concrete which could decrease durability. I would suggest a non-impact grinder.

 

[civilperson]

Prior to surface grinding, raise the Ph by application of a base solution.

 

[dik]

civilperson... why raise the pH?

Dik

 

[sennafan]

civilperson - I am also curious about the benefit of raising the ph.

GeoPaveTraffic - my one hesitation about grinding is the fear that the resulting surface might become too slippery for foot traffic in bad weather.

Thanks to both of you for the responses,

sennafan

 

[GeoPaveTraffic]

There are many types of grinders. Some leave the surface (as you fear) very smooth, others leave it very rough.

 

[civilperson]

Original post listed two or three unknown chemicals which discolored and etched the surface. Without knowing for sure, I would assume a acidic solution to produce this condition. A program of grinding will not change the acid situation, (and the continued deteriation), thus my recommendation to raise the Ph prior to repair.